A coalition of nations, led by the United States, called for an immediate cease-fire in Aleppo and condemned Russia for interfering with attempts to bring humanitarian aid to those civilians trapped in the Syrian city.

"Aleppo is being subjected to daily bombings and artillery attacks by the Syrian regime, supported by Russia and Iran. Hospitals and schools have not been spared. Rather, they appear to be the targets of attack in an attempt to wear people down. The images of dying children are heartbreaking," the group of six nations said in a statement Wednesday.

The leaders of those countries -- Canada, France, Germany, Italy, Britain, and the U.S. -- called on the Syrian government to agree to the U.N.'s plan in Aleppo and allow humanitarian aid into the city.

Syrian rebels have agreed to a five-day cease-fire to ensure the humanitarian evacuation of civilians from the eastern part of the city.

U.S. Secretary of State John Kerry is scheduled to hold talks with Russian Foreign Minister Sergey Lavrov in Hamburg, Germany later Wednesday. The two diplomats have held numerous talks in hopes of reaching a diplomatic solution to the civil war.

Kerry who was in Brussels on Tuesday to participate in his final meeting with NATO foreign ministers, said he hopes to relaunch peace talks between the Syrian regime and the opposition, but has received little help from the government of President Bashar al-Assad.

"We have been trying to find a way to get to the negotiating table ... but Assad has never shown any willingness," Kerry said. "Russia says Assad is ready to come to the table... and I am in favor of putting that to the test."

The rebels made the ceasefire proposal Wednesday morning, just hours after Syria's Russian-backed army gained control of at least three-quarters of Aleppo's Old City, which had been under rebel control since 2012.

The rebel factions are proposing that around 500 people needing urgent medical care be evacuated under the supervision of the United Nations. They are also proposing that other civilians who wish to leave be allowed to travel to rural northern Aleppo, where there is no government presence, instead of neighboring Idlib province, which is besieged by Russian airstrikes.

Civil Defense members look for survivors under rubble of damaged buildings after airstrikes on the northern neighborhood of Idlib city, Syria, Dec. 5, 2016.

The rebels say once the humanitarian situation has been alleviated, they will discuss the future of Aleppo.

There has been no response from Damascus about the rebels' offer.

The fall of Aleppo's Old City caps a major offensive launched by the army late last month to drive the rebels out of eastern Aleppo and marks a major victory for the government of President Bashar al-Assad in the now five-year-old conflict.

Parts of the historic Old City neighborhood, which was declared a UNESCO Heritage site 30 years ago, were devastated in the takeover, and witnesses say swaths of the historic sector are now virtually unrecognizable.

The Syrian Observatory for Human Rights, which monitors and reports on Syria's civil war, says 369 civilians have been killed in the offensive on east Aleppo, including 45 children. Another 92 civilians -- including 34 children -- were killed by rebel shelling on government-held west Aleppo.

This photo provided by the Syrian Civil Defense White Helmets, which has been authenticated based on its contents and other AP reporting, shows a Syrian boy sitting next to bodies after artillery fire struck the Jub al-Quba district in Aleppo, Nov. 30m, 2016.

U.N. special envoy Stefan de Mistura said last week he expected eastern Aleppo to fall to government forces by the end of December, without a negotiated settlement to end the four-year rebel occupation.

Tens of thousands of civilians are thought to be trapped in eastern Aleppo despite a huge surge of refugees fleeing in the past two weeks for the relative safety of government-controlled western districts.

Monitors last week estimated that 18,000 civilians in the east had moved into western neighborhoods and more than 9,000 others into a Kurdish-controlled district.

In a separate development, Syria's state-run SANA news agency says a military airport located west of the capital of Damascus was hit Wednesday morning by several Israeli surface-to-surface missiles. It was the second such airstrike carried out by Israeli forces on positions outside of Damascus in a week.